How lossless metadata removal works

An image file is a container. Inside it, the compressed picture sits next to separate blocks of information about the picture: where and when it was taken, the camera or software that made it, edit history, and sometimes a signed record of its origin. Exifo reads the container, lists every block, and writes a new file that leaves out the blocks you choose.

Lossless by design

Most “metadata removers” draw the picture onto a canvas and save it again. That re-compresses a JPEG or WebP, loses quality, and can drop the colour profile. Exifo never decodes the picture to produce the file you download:

1. The file is read as raw bytes, on your device.
2. The container is parsed into its segments (JPEG) or chunks (PNG, WebP).
3. A new file is assembled by copying the blocks that are kept, byte for byte, and skipping the rest.
4. The compressed image data is copied untouched.

What is found and removed

Files are flagged AI provenance found when they carry an IPTC digital source type such as trainedAlgorithmicMedia, Content Credentials that name a generative model, or generator settings in PNG text (Stable Diffusion parameters, ComfyUI prompt and workflow). Software names and credit lines are shown so you can judge them yourself.

What is always kept

Some blocks change how the picture looks, so they stay in every file:

• The colour profile (ICC), so colours look the same.
• Orientation. If the full EXIF block is removed, a 36-byte block holding only the orientation is written back. You can turn this off.
• Transparency, gamma, colour space and HDR colour information.
• Animation frames and timing (APNG and animated WebP).
• The Adobe colour-transform block in JPEG, which CMYK images need.

Phones store HDR gain maps and motion-photo videos after the end of the main JPEG, indexed by a multi-picture (MPF) block. Those offsets break when other blocks are removed, so in this version the extra images are removed together with their index. The main image is unchanged, and the file becomes a standard single-image JPEG.

Proof that nothing else changed

Every cleaned file is checked before you can download it. Exifo hashes the image data of the original and of the result with SHA-256: for JPEG the quantisation and Huffman tables, frame header and every scan; for PNG the header, palette and all image data chunks; for WebP the VP8, VP8L, ALPH and animation frame payloads. If the hashes differ, the output is thrown away and you see an error instead. You can also decode both files and compare every pixel with Compare pixels, or check any two files with Compare.

Formats

Lossless cleaning and editing work on JPEG, PNG and WebP. Convert also opens HEIC, AVIF, GIF and BMP. The image tools (Compress, Convert, Resize, Watermark) re-encode by design and are marked Re-encodes image. Rotating a JPEG without cropping or resizing only changes its orientation tag, which is lossless.

What Exifo cannot do

• It does not remove watermarks embedded in the pixels, such as SynthID, or visible watermarks. These are not metadata.
• It does not stop platforms from detecting AI content with their own classifiers.
• A cleaned file is not “undetectable”.

Removing provenance from AI-generated images can be against platform rules or the law where you live. See the terms.

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